The instant invention relates to a method for purifying hexamethyldisiloxane. More specifically the instant invention relates to a purification method which affords a very pure hexamethyldisiloxane, lacking any unpleasant smell, from the very impure hexamethyldisiloxane ultimately recovered from the trimethylchlorosilane and hexamethyldisilazane used as silylating agents in the pharmaceutical industry.
Trimethylchlorosilane and hexamethyldisilazane are widely used as silylating agents in the pharmaceutical manufacturing industry, such as in the production of antibiotics such as penicillin cephalosporin, etc. The hexamethyldisiloxane produced and recovered as a by-product from this trimethylchlorosilane or hexamethyldisilazane contains large quantities of impurities. such as organic solvents, since the silyl group protective reaction is conducted in the presence of a low-boiling organic solvent, as well as trimethylsilanol, trimethylmethoxysilane, etc.
Hexamethyldisiloxane no longer functions as a silylating agent for pharmaceutical manufacture. Also, it is technically difficult to obtain a very pure, deodorized hexamethyldisiloxane from the very impure hexamethyldisiloxane recovery liquid. The primary method of handling this recovery liquid is the distillative recovery of a major part of the organic solvent, with the residue being incinerated as an industrial waste. Even when the hexamethyldisiloxane is recovered, it has a distinctly unpleasant odor which limits its use.